A measurement of the moisture content of a non-metallic material may be required as part of a processing line. A ready example of a process requiring moisture measurement is the drying of timber in a kiln. If a measure of the moisture content of the timber is available, this can be used to control the drying time. This may result in in reduced electricity costs, which are becoming an increasingly large and volatile cost of production. Also, or alternatively, the product quality may be increased, through a reduction in the amount of under-dried product.
Various proposals have been put forward in the past in respect of moisture sensing using microwave technologies and including that invented by Wayne S Holmes, Stephen G Riley and Richard B Keam, the subject of international application PCT/NZ96/00134, published as International Publication Number WO 97/21992. Such earlier technology, whether using microwaves, capacitive or impedance systems all measured average moisture content of the timber. If the moisture content variation across the stack is to be determined, then to the present time this has required the use of sample boards, which are provided in the stack with moisture sensing probes inserted into them.
It is therefore an object of the present invention to provide an apparatus and method for moisture sensing using microwave technologies and which in the case of stacked timber will enable the moisture content of individual boards in the stack and the variation of moisture content across the stack to be determined.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.